Warm Winter Leaves Stored Corn at Risk for Mold

Before farmers go full throttle into the 2012 planting season, they would be wise to inspect what's left of their 2011 corn crop for signs of mold, says a Purdue University agricultural engineer.

Richard Stroshine said he has heard scattered reports of Indiana farmers finding higher-than-normal percentages of moldy, discolored kernels when they've removed corn from storage facilities. Elevators and other buyers of corn pay less for mold-contaminated grain, if they buy it at all.

Corn stored in bins since the fall harvest could be at a heightened threat for mold, Stroshine said. The reason? A winter that wasn't cold enough for long enough to protect the grain from fungal infection.

Moldy corn can contain toxins harmful - even fatal - to livestock. Much of the corn grown in Indiana is used as animal feed.

"Farmers should constantly be checking their grain for mold growth," Stroshine said. "If they find mold, they've got to get that corn out of the bin as soon as possible so that it doesn't spread to other grain in the bin."

A typical winter with air temperatures regularly near or below freezing allows corn to be cooled to temperatures near freezing, inhibiting mold development. That is particularly important when corn is stored at or above 15 percent moisture. This past winter saw many days above 50 degrees Fahrenheit, creating conditions more favorable for mold growth.

When mold risks are high, farmers should take steps to evenly cool the grain in the bin. A common practice, known as coring, involves taking one or more truckloads of corn from the bin and leveling the crop that remains. The process removes fine material that often accumulates in the center - or core - of the bin, filling air pockets between kernels and restricting air circulation.

To ensure even airflow distribution, farmers should maintain a level surface at the top of the bin. Without sufficient and uniform air movement in the bin, heat can build up in some areas and promote mold growth.

Farmers who cored their bins reduced the likelihood of mold problems this spring but still should keep an eye on their leftover crop, Stroshine said. Those who didn't perform coring operations will need to be even more vigilant, he said.

Bins should be visually inspected and grain temperatures monitored weekly, Stroshine said. He recommended running bin fans for 30 minutes before entering the storage facility to conduct an inspection.

"Aeration will push musty odors, which are indicative of mold growth, to the headspace of the bin," he said. "If the problems are deeper in the bin it will take longer for odors to reach the surface. So you could run the fans another 2-4 hours and check again.

"While you're in the bin, look for signs of condensation on the inside of the bin's roof. That's an indication you've had moisture generated by mold activity. Also, look for crusting on the grain's surface, which is symptomatic of mold growth."

Farmers also should check grain temperatures for mold-generated hot spots at numerous places in the grain mass, Stroshine said. If a producer does not have a temperature probe, a metal rod will do. Stroshine advised sliding the rod into the grain and pulling it out after about 15 minutes. If the rod is warm, mold could be present.

Insects that invade stored grain probably will be active earlier this year, he said.

Stroshine offered other grain bin tips:

Exercise extreme caution when entering a bin. Grain can shift and trap a farmer, leading to potential suffocation. A family member or friend should remain outside the bin to offer assistance, if needed. Shut off and tag out unloading equipment before entering a bin.

Cover bin fans when fans are not running to keep warm, humid air and rodents from entering the bin through the fan inlet. Covers can be made from plywood, sheet metal, heavy plastic or canvas.

Keep grain as cool as possible for as long as possible. If planning to hold onto corn past the middle of June, consider warming it to about 50 degrees.